The present invention relates to a vehicle control device for controlling a vehicle drive apparatus including an input member drive-coupled to an engine and a rotary electrical machine, an output member, and a transmission having a plurality of friction engagement elements, in which a plurality of shift speeds are switched by controlling engagement and release of the plurality of friction engagement elements, and a rotary driving force of the input member is shifted by a change gear ratio of one of the shift speeds and outputted to the output member.
In recent years, hybrid vehicles have been brought into practical use in which fuel efficiency of engine can be improved and exhaust gas can be reduced by using an engine and a rotary electrical machine in combination as driving force sources. As an example of a vehicle drive apparatus used in such a hybrid vehicle, Japanese Patent Application Publication No. JP-A-2008-094332 listed below describes a vehicle drive apparatus structured to shift the rotary driving force of the engine and the rotary electrical machine as driving force sources by the change gear ratio of one of shift speeds set in a transmission and output the shifted driving force.
In such a drive apparatus for hybrid vehicle, when the vehicle turns to a coast state by removing a foot from the accelerator pedal, switching to a shift speed with a smaller change gear ratio (upshift) may be performed depending on the relation to the vehicle speed, and so on. Here, when the shift speed is switched between two adjacent shift speeds, engagement and release of friction engagement elements are controlled to perform what is called a changeover shift. In this changeover shift, normally, the friction engagement element on the release side is fully released relatively quickly in an initial stage of the shift operation, and the friction engagement element on the engagement side is engaged gradually while slipping. Negative torque acting on the input member is small in an ordinary vehicle which has only the engine as the driving force source, and even in a hybrid vehicle when the rotary electrical machine is not performing regeneration, or the like. When such shift control is performed, the rotation speed of the input member merely decreases by friction forces of respective parts in the engine and the like, and changes gently. Therefore, there hardly occurs a problem of generation of shock (shift shock) when the friction engagement element on the engagement side is engaged.
When the vehicle is in the coast state, braking may be performed subsequently by the intention of the vehicle driver. In this situation, in the drive apparatus for hybrid vehicle as described above, braking of the vehicle may be performed by causing the rotary electrical machine to perform regeneration. In the case where the rotary electrical machine performs regeneration, the rotary electrical machine outputs and transmits relatively large negative torque to the input member. Thus, when the usual changeover shift as described above is performed, the rotation speed of the input member is decreased largely by the negative torque outputted by the rotary electrical machine and changes rapidly, and it is highly possible to generate shift shock. Accordingly, the vehicle drive apparatus described in Japanese Patent Application Publication No. JP-A-2008-094332 is structured to limit the magnitude of the negative torque (regeneration torque) outputted by the rotary electrical machine to a certain magnitude or smaller when performing regeneration. Thus, generation of shift shock in the vehicle due to a rapid drop of the rotation speed of the input member drive-coupled to the rotary electrical machine is suppressed.